It may look like a forgotten military landscape, decaying beneath an elevated freeway and overgrown with weeds, but hidden below the abandoned buildings and broken pavement, Presidio planners see the potential to regenerate a wetland.

Quartermaster Reach is currently so neglected, most people don't even know it exists. Floating between Lucasfilm's Letterman complex and the Presidio Post Office, some sections have been abandoned for decades. A disused power plant sits at one end, and piles of dirt and construction debris mark the northern edge. Once home to Yelamu Ohlone, Mexican settlers commandeered the area's flow of fresh water in the 1700s, the military established a shooting range on the site in the 1800s and paving for Doyle Drive erased the site's history by the 1930s.

But Doyle Drive may hold the key to the 9.5-acre site's restoration. Nearing the century-mark, the elevated freeway is currently being replaced with a slightly-lower-impact Presidio Parkway. When construction is complete, the landscape underneath the freeway may transform from asphalt to wetland.

The key to revitalizing the area is a stream flowing deep beneath the site. Starting at the El Polin Spring, where drinking the water was once said to enhance virility, it flows under Lover's Lane Bridge before disappearing into decades-old storm drains beneath a bramble. The stream re-emerges briefly in Thompson Reach, before entering a 72-inch culvert that empties into Crissy Marsh.

The site is well suited for a wetland, with silt and clay comprising most of the native soil. The curve of the roadway will maximize natural light for plants and animals, and with improved tidal exchanges and continuous green space, the wildlife corridor will be significantly expanded, though still interrupted by a massive elevated freeway.

Earlier this summer, the Presidio Trust completed a Quartermaster Reach Environmental Assessment and identified three potential treatments: a minimally constructed stream, a diverse wetland with a boardwalk trail or a tidal lagoon.

The wetland is the preferred alternative for simultaneously enhancing habitat, providing public access and recognizing historic features.

A long-forgotten rail line that once connected the Marina to Fort Mason is a crucial element of the site. Those tracks, a section of which still exists today beneath Mason Street, would be commemorated with historic markers.

Transit enthusiasts may dream of a day when Mason is converted into a rail line, perhaps as an extension of the tracks currently traveled by the F-line, but there are currently no concrete plans to do so. Earlier this year, Supervisor Alioto-Pier criticized a proposal to extend the F to Fort Mason, citing bogus concerns about outreach and funding.

In addition to providing a path for wildlife, the restoration would facilitate the creation of a new "Tennessee Hollow Corridor," originally called for in the Presidio's Trails and Bikeways Plan. The corridor would connect playgrounds and sports fields at the southern end of the Presidio to Crissy Marsh, providing a continuous path from Lincoln Avenue to Mason Street.

So far, the project has attracted enthusiastic support. When public comment closed on Aug. 1, all letters received were in support, and the Presidio Trust expects to start work quite soon.

"We'll be responding to the comments shortly," said Presidio spokesman Clay Harrell, "and we'll release the final report as soon as next week, along with the signed finding of No Significant Impact." Due to the involvement of the National Park Service, Caltrans and the State Historic Preservation Office, complications with interagency cooperation could arise, but all agencies are currently working in sync, according to Harrell. He estimated the initial construction on culverts and utilities could begin in as little as a month.

The Presidio Parkway construction will require a temporary bypass on the site until 2013, so it'll be a few years before the project is fully implemented. But once it's finished, Presidio guests and residents — human, plant, and animal — will enjoy one more piece in the jigsaw puzzle that is the restoration of the Presidio.